Robots are used throughout the manufacturing industry and their use is gradually expanding to service areas. Particularly, robots are used in manufacturing at industrial sites and at service sites, and the driving range of the robots is overlapped with the human activity areas, thus driving safety of the robots in overlapping areas is important.
Accordingly, various robot safety technologies have been developed to minimize damage caused by collision in overlapping activity areas between human and robot. As an example of these safety robot technologies, variable stiffness joint system is becoming an important core technology.
Realizing a high-efficiency robot joint system that achieves high efficiency at low cost is also one of the big tasks of robot research. It is necessary to develop a high-performance robot joint system that meets the needs of precise positioning control performance and safe contact work performance at the same time.
As an example of a variable stiffness robotic joint system, “Driving device” has been disclosed in Japanese Patent Application Publication No. 2014-046417, in which the stiffness of the rotation direction of a joint is adjusted by using a spring.
As another example, “Double actuator unit, double actuator apparatus having the same, and control method thereof” has been disclosed in Korean Patent No. 10-0835908, in which a joint is rotated and the stiffness is adjusted by using two motors.
However, the technology disclosed in the document of Korean Patent is disadvantageous in that since one motor is only involved in the rotation of the joint, and the other motor is only involved in the stiffness control, joint motion is determined only by the output of one motor while using two motors, and the other motor is used only for adjustment of stiffness, so it is not efficient for motor use.